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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 6th Apr 2020, 9:22 am   #1
vinrads
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Default Info regarding reaction controls.

I am attempting to re assemble this cap/resistor reaction control , can anyone tell me which way would it be ie max resistance at min capacitance or max capacitance? Thank's Mick.
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Old 6th Apr 2020, 12:42 pm   #2
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Default Re: Info regarding reaction controls.

I presume this is the Ultra Tiger and I cannot find a circuit that shows a combined variable capacitor/resistor reaction control. If the variable resistor is a low value wirewound it is probably in the cathode resistor for V2 giving maximum gain when set to the lowest value, the capacitor could do either depending on the circuit.
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Old 6th Apr 2020, 12:53 pm   #3
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Default Re: Info regarding reaction controls.

I think this query relates to this thread:-

https://www.vintage-radio.net/forum/...d.php?t=165377
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Old 6th Apr 2020, 1:24 pm   #4
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Default Re: Info regarding reaction controls.

Ah Sorry I should have said the set is a Pye 808 battery set ,the resistor is in the heater of the first valve ,acting as a gain control , Mick.
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Old 6th Apr 2020, 1:41 pm   #5
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Default Re: Info regarding reaction controls.

And the capacitor controls the amount of reaction, more capacitance = more reaction.
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Old 6th Apr 2020, 5:47 pm   #6
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Default Re: Info regarding reaction controls.

So would you need full heater volts for more reaction, or less heater volts?

I have it working. It is still noisy on the capacitor side, I went for full heaters at lowest capacitance.

Mick.
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Old 7th Apr 2020, 7:48 am   #7
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Default Re: Info regarding reaction controls.

I am not an expert but I would expect more reactance to occur with more capacitance as it is a type of positive feedback.
Lowering the capacitance would lower the volume. Likewise lowering the heater volts would also lower the efficiency of the valve having a similar effect. So I would assume lower resistance goes with lower reactance.
But I may be wrong.

I wonder why this thread was not moved to the original thread in the radio section.

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Old 7th Apr 2020, 8:52 am   #8
vinrads
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Default Re: Info regarding reaction controls.

Hi Mike I started a new thread in the radio section, to see if I could get some interest ,then it was moved here , I have no problem with that , are you saying higher capacitance goes with lower resistance ,that's my thinking .
I am getting used to assembling the unit now I must have done it six times at least , still having problems with int short circuit ,thinking about making some different insulating disks , Mick.

Last edited by vinrads; 7th Apr 2020 at 8:59 am.
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Old 7th Apr 2020, 12:17 pm   #9
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Default Re: Info regarding reaction controls.

Quote:
Originally Posted by crackle View Post
I am not an expert but I would expect more reactance to occur with more capacitance as it is a type of positive feedback.
Lowering the capacitance would lower the volume. Likewise lowering the heater volts would also lower the efficiency of the valve having a similar effect. So I would assume lower resistance goes with lower reactance.
But I may be wrong.

I wonder why this thread was not moved to the original thread in the radio section.

Mike
That sounds backwards- a lower resistance in the heater circuit will give more emission and presumably more gain.

Which way round the C-R interact would depend on whether the effects were required to be additive or subtractive. Given the endless historic discussions about the difficulties with achieving smooth reaction control, it may be that making the resistor greater (less gain) as the capacitor value increased (more positive feedback) was useful to tame things.
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Old 7th Apr 2020, 3:08 pm   #10
vinrads
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Default Re: Info regarding reaction controls.

That's rely confused thing now ! Having tried making new insulators which worked,for a while ,I think I need to locate a replacement . Mick.
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Old 7th Apr 2020, 5:12 pm   #11
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Default Re: Info regarding reaction controls.

Quote:
Originally Posted by Herald1360 View Post
Quote:
Originally Posted by crackle View Post
I am not an expert but I would expect more reactance to occur with more capacitance as it is a type of positive feedback.
Lowering the capacitance would lower the volume. Likewise lowering the heater volts would also lower the efficiency of the valve having a similar effect. So I would assume lower resistance goes with lower reactance.
But I may be wrong.

I wonder why this thread was not moved to the original thread in the radio section.

Mike
That sounds backwards- a lower resistance in the heater circuit will give more emission and presumably more gain.

Which way round the C-R interact would depend on whether the effects were required to be additive or subtractive. Given the endless historic discussions about the difficulties with achieving smooth reaction control, it may be that making the resistor greater (less gain) as the capacitor value increased (more positive feedback) was useful to tame things.
Chris, you are so right, what a silly mistake. For some reason I was thinking lower volts on heater and wrote about lower resistance.
thanks for correcting it.
Mike
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Old 7th Apr 2020, 5:19 pm   #12
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Default Re: Info regarding reaction controls.

If the picture in the linked thread is taken literally, reaction and volume both increase clockwise, so turning clockwise should increase capacitance and reduce resistance.
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